Treatment of human head lice

The treatment of human head lice is a process for removing head lice parasites from human hair and it has been debated and studied for centuries. However, the number of cases of human louse infestations (or pediculosis) has increased worldwide since the mid-1960s, reaching hundreds of millions annually.[1] There is no product or method which assures 100% destruction of the eggs and hatched lice after a single treatment. However, there are a number of treatment modalities that can be employed with varying degrees of success. These methods include chemical treatments, natural products, combs, shaving, hot air, and silicone-based lotions.

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The American Academy of Pediatrics states treatment for head lice should never be initiated unless there is a clear diagnosis for head lice since all treatments have potential side effects.[2]

Lice eggs hatch 6–9 days after oviposition. Therefore, a common recommendation is to repeat treatment with a pediculicide at least once after 10 days, when all lice have hatched.[3] Between the two treatments (Days 2–9) the person will still be infested with lice that hatch from eggs not killed by the anti-louse product. Between the treatments, it is advised[by whom?] to wet the hair and comb daily with a louse-comb to remove the hatching lice.

If no living lice are found, the treatment was successful, even if nits/eggs are visible on the hair. If living lice are still present, repeat the treatment using an anti-louse product with a different active ingredient. Prophylactic treatment with pediculicides is not recommended.[4] Itching may persist for up to a week after head lice eradication.[citation needed]

Devices blowing heated air onto the scalp have been tested for efficacy in killing lice and eggs and shows up to 98% mortality of eggs and 80% mortality of hatched eggs. The louse loses body moisture to the heated air and within the treatment period becomes desiccated and dies.[5] Currently, there is only one FDA approved medical device that offers this technology.[6]

A standard home blow dryer will kill 96.7% of eggs with proper technique.[6] To be effective, the blow dryer must be used repeatedly (every 1 to 7 days since eggs hatch in 7 to 10 days) until the natural life cycle of the lice is over (about 4 weeks).[citation needed]

A special fine tooth comb that can pick out lice is used. For a treatment with louse comb alone, it is recommended to comb the hair for an hour to an hour and a half (depending the length and type of the hair) daily or every second day for 14 days. Wetting the hair especially with water and shampoo or conditioner will facilitate the combing and the removal of lice, eggs and nits.[7][8][9][10]

Electronic lice combs use a small electrical charge to kill lice. The metal teeth of the comb have alternating positive and negative charged tines, which are powered by a small battery. When the comb is used on dry hair, lice make contact with multiple tines of the fine-toothed comb, thereby closing the circuit and receiving an electrical charge. A non-peer-reviewed letter has been published in a dermatology journal claiming effectiveness based on personal experience (total of 6 uses).[11] Those with long or fine hair, the metal long tooth combs seem to snag and pull hair. Metal combs are better for thick hair. Plastic short tooth combs best used for treating long and fine hair.

The only agents approved by the FDA for treatment of pediculosis are topical ivermectin lotion, lindane, and malathion.[13][needs update]Tea tree oil has been promoted as a treatment for head lice; however, evidence of its effectiveness is weak.[14][15] A 2012 review of head lice treatment recommended against the use of tea tree oil for children because it could cause skin irritation or allergic reactions, because of contraindications, and because of a lack of knowledge about the oil's safety and effectiveness.[16] Other home remedies such as putting vinegar, isopropyl alcohol, olive oil, mayonnaise, or melted butter under a shower cap or plastic bag have been disproven,[17] and may be dangerous.[18] Similarly, the Centers for Disease Control and Prevention reports that swimming has no effect on treating lice, and can in fact harm the treatment by commercial products.[19]

The journal Pediatrics has published a study in which lice can be killed by suffocating them using a non-toxic face cleanser to effectively "shrink wrap" them over an extended period of time achieving a success rate of roughly 95%. The procedure in the study used application of the product Nuvo lotion (Cetaphil) thoroughly combed in with a regular comb and blow dried, and then hair was shampooed after 8 hours. This was repeated once per week for 3 weeks using two study groups: one that followed up by removing nits and the other that did not. There was no appreciable difference in success rates in the groups. In its conclusion, the Journal stated, "Dry-on, suffocation-based, pediculicide lotion effectively treats head lice without neurotoxins, nit removal, or extensive house cleaning. These results are comparable or superior to the results previously reported for treatments with permethrin, pyrethrin, and malathion."[20]

Shaving the head or cutting the hair extremely short can be used to control lice infestation. Short hair, baldness, or a shaven scalp are generally seen as a preventive measure against lice infestation. This will also eliminate – particularly if maintained for the length of the parasites' reproductive cycle – lice infestation. Infestation with lice is not a disease and the medical symptoms are normally minimal. In any case, health providers and parents should try not to create emotional problems for children during examination and treatment.[21] Shaving of the area above and behind the ears and the upper part of the neck while leaving the crown of the head with hair is commonly used to prevent lice among tribes in Africa, Asia, and America (in America – Mohawk style).[citation needed]

Schools in the United States, Canada, and Australia commonly exclude infested students, and prevent return of those students until all lice, eggs, and nits are removed.[22] This is the basis of the "no-nit policy". Data from a primarily American study during 1998–1999 found that no-nit policies were present at 82% of the schools attended by children suspected of louse infestation.[23] A separate 1998 survey revealed that 60% of American school nurses felt that "forced absenteeism of any child who has any nits in their hair is a good idea."[24]

Head louse nits on human hair

A number of health researchers and organizations object to the no-nit policy.[22][25][26][27] Opponents to the no-nit policy mention that visible nits may only be empty egg casings which pose no concern as transmission can only occur via live lice or eggs.[22] This has led to the perception that the no-nit policy serves only to ease the workload of school nurses and punish the parents of infested children.[22]

Proponents of the no-nit policy counter that only a consistently nit-free child can be reliably shown to be infestation-free.[28] That is, the presence of nits serves as an indirect proxy for infestation status. Proponents argue that such a proxy is necessary because lice screening is prone to false negative conclusions (i.e., failure to find lice present on actively infested children).[25][29] For example, a 1998 Israeli study found that 76% of live lice infestations were missed by visual inspection (as verified by subsequent combing methods).[30][31] Although lice cannot fly or jump, they are fast and agile in their native environment (i.e., clinging to hairs near the warmth of the scalp),[25] and will try to avoid the light used during inspection.[32][33] Lice colonies are also sparse (often fewer than 10 lice), which can contribute to difficulty in finding live specimens.[34] Further, lice populations consist predominantly of immature nymphs,[35] which are even smaller and harder to detect than adult lice.[30]